The oxidation-reduction chemistry of manganese (II, III, IV) complexes is to be investigated by electrochemical, spectroscopic, magnetic, and stopped-flow methods in aprotic solvents. One goal of the research is to discover manganese complexes and solution conditions which result in oxidation-reduction chemistry that mimics that of mitochondrial superoxide dismutase (SOD), of the water-oxidizing species associated with photosystem II in green-plant photosynthesis, and of nuerological manganese. The ligands proposed for study are 3,5-di-tert-3,5-di-tert-butylcatechol, 2,2'-bipyridine, o-aminophenol, triethanolamine, pyrophosphate ion, sorbitol, catecholamine, C-DOPA, and 8-quinolinol. Determination of the oxidation-reduction thermodynamics, reaction kinetics, and solution structures for the various manganese complex-solvent systems will be the means of characterization. Studies of the reaction chemistry and the chemistry of the reaction products for the various manganese complexes in combination with O2, O2, and H2O2 are a major part of the project. The oxidation-reduction potentials for manganese, iron and copper-zinc superoxide dismutases will be determined. The EXAFS method will be used to determine the geometry and bonding of the coordination sphere about the manganese cofactor of photosystem II will be prepared and evaluated in relation to the efficient oxidation of H2O to O2.